Intraocular lenses generally comprise an optic and one or more haptics, and are typically placed in the lenticular capsule, to replace the natural lens. Many types of such intraocular lenses and configurations are known. Unsatisfactory placement or degradation of the lens, or degradation of the eye such that the lens is no longer especially effective, cannot readily be ameliorated by lens replacement.
It is also known to introduce a secondary lens in the sulcus. For example, a “multi-focal piggyback lens” is available from Zeiss under the name Acor®, and is intended for the simultaneous correction of residual ametropia and presbyopia. It comprises a convexo-concave optic, wherein both faces of the optic are curved in the same sense with respect to the plane defined by the rim of the optic, and haptics which lie in that plane. The distal ends of the haptics are intended to come into contact with the ciliary sulcus, typically at a diameter of 12.5-13.5 mm.